Molding systems, such as the Thixosystem manufactured by Husky Injection Molding Systems Limited, are used for molding parts made from a metallic-molding material, such as (but limited to) magnesium, aluminum, and/or zinc, (or alloys thereof), etc. Some molds define a complicated mold cavity that may be difficult to fill with the metallic-molding material because the metallic-molding material needs to be handled at a very hot operating temperature (such as, 1075 degrees Fahrenheit or 580 degrees Centigrade) and then it needs to be cooled down to a temperature that is significantly lower than the operating temperature.
A critical issue with filling the mold with the metallic-molding material is whether there is sufficient “pack-out” pressure applied to the metallic-molding material to pack out the mold. The pack-out problem usually leads to defects in a molded part, such as shrinkage-porosity defects and/or flow defects. For example, magnesium experiences a reduction of approximately 10% in volume when the magnesium changes from a molten state to a solid state. To overcome this difficulty, a sufficient pack-out pressure must be applied to the metallic-molding material after the mold is filled. However, molds usually have complicated geometries and it is very difficult to ensure pack out of the mold. If a first section of the mold becomes filled before a second section of the mold is filled, the first section will become packed out under a significantly lower pressure because the second section has not yet been filled. The first section will shrink significantly and will have a lower density in comparison to the second section because the second section will experience a pack out pressure that was not experienced by the first section.
The following is a summary of potential art that does not appear to provide a solution to the above-mentioned problem of packing out molds with a metallic-molding material. Resin-based molding materials are not analogous to metallic-molding materials because metallic-molding materials (i) have a low heat capacity such that heat flows quickly from the metallic-molding material over to molding-system components, while in sharp contrast, resin-based molding materials have a high heat capacity such that heat flows slowly from the resin-based molding material over to molding-system components, and (ii) metallic-molding materials are melted at significantly higher temperatures in sharp contrast to the temperatures at which resin-based molding materials are melted.
U.S. Pat. No. 5,762,855 (Inventor: Betters et al; Published: Jun. 9, 1998) discloses molding of large components for use in automotive bumpers by using a sequential fill valve gated injection molding system operative on plastic-resin-based molding material.
U.S. Pat. No. 6,875,383 (Inventor: Smith et al; Published: Apr. 5, 2005) discloses injection molding of a molten material by sequentially injecting the molten material into mold cavities at a rate to fill and pack the cavities with the molten material, and then holding the molten material in the mold cavities. The methods and devices appear to be effective to reduce the clamping force needed to clamp multiple cavity molds.
U.S. Pat. No. 6,099,767 (Inventor: Tarr et al; Published: Aug. 8, 2000) discloses an injection mold bushing having central passageway for shut-off gate pin and separate passageway for injecting molten plastic. The wear bushing is positioned at the outlet end of the mold bushing to protect it from wear from the molten plastic and to direct the plastic through a tip orifice.
U.S. Pat. No. 6,767,486 (Inventor: Doughty et al; Published: Jul. 27, 2004) discloses an injection molding system that includes a controller to control rate of material flow through first runner independently of second runner.
The following references appear to be applicable to systems and components for molding metallic-molding materials, but they appear to not resolve the problem of pack out of metallic molding material held in a mold.
PCT Patent No. WO 2004/078383 A1 (Inventor: Manda; Published: Sep. 16, 2004; Assignee: Husky Injection Molding Systems Limited, Canada) discloses a sprue apparatus for injection molding or die-casting machine. The sprue apparatus has a nozzle connection interface, a melt duct, a mold-connection interface, and thermal regulators for regulating thermal zones that segment length of the sprue apparatus.
European Patent No. 1,101,550 A1 (Inventor: Massano et al; Published: May 23, 2001; Assignee: Plasthing Services S.r.l., Italy) discloses a mold for injection molding of e.g. magnesium, magnesium alloy. The mold has electrical resistors arranged for heating feed socket, distribution plate, injectors and spacer elements.
PCT Patent No. WO 2005/110704 A1 (Inventor: Manda et al; Published: Assignee: Husky Injection Molding Systems Limited, Canada) discloses a molding-machine-melt-conduit coupler useful in a runner system and in an injection-molding machine. The coupler includes coupling structure having surface coupling with two melt conduits and cooling structure to provide coolant to coupling structure.
U.S. Pat. No. 6,938,669 (Inventor: Suzuki et al; Published: Sep. 6, 2005; Assignee: Denso Corporation, Japan) discloses injection molding of metal products that involves heating tip of hot runner, spraying lubricant onto molding surface and metering material, simultaneously between mold clamping and pressurizing processes.
U.S. Pat. No. 6,533,021 (Inventor: Shibata et al; Published: Mar. 18, 2003; Assignee: Ju-Oh Inc., Japan) discloses a metal mold of hot runner type injection molding machine and method of manufacturing the metal mold.